High-Yield Graphene/Cellulose Nanocrystal Hybrid Material for Robust and Conductive Composite Hydrogels with Tunable Strain Sensing Capability

Graphene has been widely recognized as an effective filler in conductive hydrogels due to its remarkable electrical conductivity and exceptional mechanical strength, which are critical for developing advanced wearable strain sensors. Nevertheless, the pursuit of high efficiency and environmentally friendly strategies for graphene exfoliation still remains a formidable challenge. Herein, we proposed a novel method for high-yield preparation of graphene by combining NaHCO3 pretreatment and cellulose nanocrystal (CNC)-assisted liquid-phase exfoliation. It was found that the exfoliation yield of graphite after three rounds of pretreatment increased by 2.2 times that of untreated graphite, achieving a yield of 31%. Moreover, the incorporation of CNC further improved the exfoliation yield by 4.6 times compared to that without CNC. The resultant graphene/CNC (LEG/C) hybrid material was subsequently integrated as a filler into polyacrylamide (PAM) hydrogels, producing a composite hydrogel with ultrahigh tensile properties (with a maximum elongation at break of 3000%) and excellent sensing performance (sensitivity factor GF = 2.7 at 300% strain while maintaining high sensitivity at 5% strain). This work presents a nearly pollution-free and cost-effective approach for graphene exfoliation and develops a robust conductive composite hydrogel with tunable strain sensing capability, showcasing significant promise in the realm of advanced wearable electronics.